The present invention relates to a ratcheting mechanism, and more specifically to a ratcheting mechanism for use in a hand-held tool.
Screwdrivers and other hand-held tools are often utilized to insert, remove and/or adjust fasteners attached to various items. The tool is used to rotate the fasteners into or out of apertures in the items to properly position the fasteners with respect to the items.
In order to make the rotation of the fasteners easier when utilizing these tools, the tools often include ratcheting mechanisms which enable the tool to apply a force to the fastener when the tool is rotated in one direction, and to allow the tool to rotate freely without applying a force to the fastener in the opposite direction. Ratcheting mechanisms of this type take various forms, such as those disclosed in U.S. Pat. Nos. 5,613,585; 5,619,891; 5,778,743; 5,873,288; and 5,943,755. In each of these mechanisms, a pair of pawls are disposed within a housing for the tool. The pawls can be selectively engaged and disengaged from a toothed gear disposed within the tool housing in order to enable the gear to rotate in a specified direction to achieve the desired mechanical advantage when adjusting, inserting or removing a fastener.
However, while tools incorporating ratcheting mechanisms of this type are useful in adjusting, inserting and removing fasteners from various items, the mechanisms also have certain drawbacks. For example, due to the shape of the pawls and the corresponding placement of the pawls within the housing, prior art ratcheting mechanism constructions are unable to handle large amounts of torque without the teeth on the gear slipping past the pawls. Thus, for fasteners that are very tightly engaged with an item, mechanisms of this type effectively cannot be used to adjust, insert or remove the fasteners. Additionally, due to the large size and consequent spacing of the teeth on the gear, the tool must be rotated more than approximately 10xc2x0 in order to advance the ratcheting mechanism to the next locking position. In situations where precise movements of a fastener are necessary, the tools incorporating mechanisms of the above-referenced type with gears of this size are not suitable as these mechanisms are very xe2x80x9ccoarsexe2x80x9d and do not allow for precise movements of the fastener. Further, the prior art ratcheting mechanisms require a large number of parts to be assembled within the housing in order to complete the ratcheting mechanism, increasing the time and expense necessary for manufacturing tools incorporating these prior art ratcheting mechanisms.
Therefore, it is desirable to develop a ratcheting mechanism for hand-held tools that has a simple and easy to assemble construction, and that also provides the tool with the ability to easily and precisely adjust the position of a fastener on an item, no matter how securely the fastener is engaged with the item.
It is an object of the present invention to provide a ratcheting mechanism for a tool in which the pawls for the ratcheting mechanism are rotatably retained within elongate, arcuate slots positioned in a housing for the mechanism to enable the mechanism to accommodate large amounts of torque exerted on the mechanism without the mechanism slipping on the fastener.
It is another object of the present invention to provide a ratcheting mechanism for a tool in which the biasing members used to maintain the pawls in engagement with a toothed gear in the mechanism have an easily-assembled construction.
It is a further object of the present invention to provide a ratcheting mechanism for a tool in which the pawls and the biasing members are reliably positioned and retained within spaces formed directly in the housing for the mechanism without the need for any additional fasteners.
It is still another object of the present invention to provide a ratcheting mechanism for a tool including a rotatable gear having a large number of reduced-size teeth that allow the rotation of the mechanism and an associated fastener to be precisely controlled in order to accurately position the fastener.
It is still a further object of the present invention to provide a ratcheting mechanism for a tool which can be incorporated into a wide variety of tools for use in various applications.
The present invention is a ratcheting mechanism for use in a hand-held tool that is utilized to rotate a fastener, such as a screw, nail or bolt, among others, with regard to an item or object in which the fastener is positioned. The mechanism includes a housing that can be attached to or formed as part of a handle that is grasped in order to use the tool. The mechanism further includes a rotatable, toothed gear disposed within the center of the housing that is engaged by a pair of pivotable pawls disposed on opposite sides of the opening. The teeth on the gear are sized and positioned such that the gear need only be rotated a small distance in order to result in a displacement of one full tooth on the gear, i.e., to a successive locking position for the gear.
The pawls on each side of the gear are preferably formed as elongate members that each include a generally circular stem and an arm extending outwardly from the stem that is engageable with the teeth on the gear. The stem is received within an arcuate portion of one of a pair of slots disposed on opposite sides of the gear. The arcuate portions of each slot enclose an angle of greater than 180xc2x0 such that the stem of each pawl is reliably held within, yet allowed to pivot, easily with respect to, the slot. Each pawl is biased into engagement with the teeth on the gear by a biasing member positioned adjacent the slot and in engagement with the pawl. The biasing member is preferably formed by a pin inserted into an opening in the housing and into engagement with a biasing element extending between the hole for the pin and the slot for the pawl that contacts and biases the pawl into engagement with the gear.
The direction of the rotation of the gear within the housing is controlled by a cap rotatably connected to the housing over the pawls, the biasing members and the gear. The cap includes a pair of opposed recesses that are positioned over the housing in alignment with the pawls. When the cap is rotated in one direction or the other, one of the recesses engages the adjacent pawl to urge the pawl out of engagement with the gear against the bias of the biasing member. Further, because the cap includes a pair of recesses, each selectively engageable with one of the pawls, the cap allows the gear to be rotated in both a clockwise and counterclockwise direction with respect to the housing such that the mechanism allows for driving and removal of the fastener. The cap can also be positioned with respect to the housing such that both pawls are positioned in engagement with the gear in order to maintain the gear in a stationary position within the housing.
Numerous other features, objects and advantages of the present invention will be made apparent from the following detailed description taken together with the drawings.